Field of the Invention
The invention relates to a transparent substrate especially made of a stiff mineral material such as glass, said substrate being coated with a thin-film multilayer comprising one or more functional films able to act on solar radiation and/or long-wavelength infrared radiation.
The invention more particularly relates to a substrate, especially a transparent glazing substrate, equipped with a thin-film multilayer comprising “n” metal functional films, especially functional films based on silver or a metal alloy containing silver, and of “(n+1)” antireflection coatings, where n is an integer ≥1, in alternation, the or each functional film being placed between two antireflection coatings. Each antireflection coating comprises at least one antireflection film, each coating preferably being composed of a plurality of films, at least one film of which, or even each film of which, is an antireflection film. Here, the concept “antireflection film” is synonymous with the concept “dielectric film”; the concept “dielectric film” above all being used in contrast to the concept “metal functional film”, the metal nature of such functional films meaning that they cannot be dielectric.
The invention more particularly relates to the use of such substrates in the manufacture of thermally insulating and/or solar-control glazing units. These glazing units may be intended to be used in buildings or vehicles, especially with a view to decreasing the need for air conditioning and/or preventing excessive overheating (what are referred to as “solar-control” glazing units) and/or to decreasing the amount of energy dissipated toward the exterior (what are referred to as “low-E” glazing units) as a result of the continuing increase in the square footage of glazed areas in buildings and vehicle passenger compartments.
These substrates may in particular be integrated into electronic devices, the multilayer then possibly being used as an electrode to conduct a current (lighting device, display device, photovoltaic panel, electrochromic glazing unit, etc.), or may be integrated into glazing units having particular functionalities, such as for example heated glazing units.
Description Of The Related Art Including Information Disclosed Under 37 CFR 1.97 And 1.98
One type of film multilayer known to provide substrates with such properties is formed with a functional metal film having reflective properties in the infrared and/or with respect to solar radiation, especially a metal functional film based on silver or a metal alloy containing silver or made entirely of silver.
In this type of multilayer, the functional metal film is thus located between two antireflection dielectric coatings, each of which in general comprises a plurality of films each of which is made of an antireflection material—either a nitride (especially aluminum or silicon nitride) or an oxide.
A blocker coating is however sometimes inserted between one or each antireflection coating and the functional metal film, the blocker coating located under the functional film, i.e. on the same side as the substrate, protecting the functional film during any high-temperature heat treatments, such as bending and/or tempering heat treatments, and the blocker coating located on the functional film, i.e. on the side opposite the substrate, protecting this layer from possible degradation during the deposition of the upper antireflection coating and during any high-temperature heat treatments, such as bending and/or tempering heat treatments.
At the present time, it is generally desired for each metal functional film to be a complete film, i.e. for the entirety of their area and the entirety of their thickness to consist of the metal material in question.
For a given material (silver for example) and under deposition conditions that are conventional for this material, a complete film is considered to be obtained by those skilled in the art only once a certain thickness has been deposited.
The adhesion energy between a complete silver film and antireflection films is very low, of about the order of 1 J/m2, and the adhesion energy between two anti-reflection films is 5 to 9 times higher than that between silver and an antireflection film. The adhesion energy of a multilayer comprising at least one functional film made of silver or based on silver is therefore limited by the low adhesion energy between complete metal functional films and other materials.